The overall aim of this project is to test the hypothesis that the onset of puberty is linked to the development of the capacity of the young animal to link its biological clocks to the control of ovarian function. To accomplish this end, this set of experiments involves a detailed analysis of the appearance of biological rhythms in individual rats and whether differences in the age at which rhythms appear will correlate with the time of puberty. The second part of this project is to study two models of delayed puberty onset. One of these is an animal with growth hormone (GH) deficiency induced by infection with plerocercoid larvae of the tapeworm Spirometra. This organisms releases a substance called plerocercoid growth factor (PGF) that mimics many of the effects of endogenous GH but suppresses the secretion of GH from the pituitary. The other model is the ethanol-treated rat. If rats are given 5% (w/v) ethanol in tap water as their only drinking fluid from weaning age on, puberty is delayed. Both of thse models will be studied to determine if rhythmicity shifts are correlated with delayed puberty and to test whether puberty is delayed because of effects directly on the ovary or at the level of the brain-pituitary control system.